Production of linear polyamides



Patented Apr. 4, 1950 UNITED STATES. PATENT OFFICE PRODUCTION OF LINEAR, POLYAMIDES Sidney James Allen and James Gordon Napier Drewitt, London, England, assignors, by mesne assignments, to Celanese Corporation of America, a corporation of Delaware No Drawing. Application July 2c, 1945, Serial 1 Claim. 1

This invention relates to improvements in the production of polymeric materials, and is more In Great Britain September 30,

In the production of linear polymers, for example linear polyamides, it has generally been considered essential to start with reagents containing two and only two reactive radicles. The presence of a third or a third and fourth reactive radicle normally leads to three-dimensional polymers which, if of suflicient molecular weight,

are insoluble in all solvents and cannot be made fibre-forming. We have found that very valuable linear polyamides having in their structure rings containing carboxylic amide groups may be built up from monomeric materials, some at least of which contain more than two amide-forming groups, by using starting materials having their reactive groups in particular positions. We have found that by this means the production of threedimensional polymers may be avoided and linear condensation products suitable, for example, for

If the number of amide In order that the number of amide nitrogen atoms shall be at least equal to the number of amide carbonyl groups, the numberof carboxylic acid groups or their equivalent present in the reaction mixture (neglecting any small quantities of substances which may be used for the stabilisation of the viscosity of the polymers) should not exceed the number of amino groups present.

The carboxylic amide-containing rings may contain one or two nitrogen atoms. Those containing one nitrogen atom will have one carbonyl group, while those containing two nitrogen atoms may have either one or two carbonyl groups.

The rings may have a number of different structures. For example, they may be ketopiperazine rings, and particularly 2.5-diketo and 2-keto piperazine rings (the polymers containing 2.3-dlketopiperazine rings are more particularly described in application S. No. 583,841); they may have ketopyridazine rings, and particularly 3.6- diketo-pyridazine; they may have ketopyrimidlne or keto-hydro-pyrimidine rings, and particularly 2.4-diketo-hexahydro-pyrimidine (hydro-uracil),

polymers containing 2-keto-hexahydro-pyrimi-' dine rings being described in the said application S. No. 583,841; they may have ketopyrazolidine and pyrazoline rings, for example 3.5-diketopyrazolidine and 3- or 5-keto-pyrazoline (pyrazolone); they may have keto-imidazoline rings, for example 2.4-diketo-imidazoline (hydantoin), polymers containing 2-keto-imidazoline rings being described in application S. No. 583,841; or they may have ketopyrrolidine or ketopiperidine rings, that is to say 7- or o-lactam rings.

- The new polymers are composedof a series of such carboxylic amide-containing rings linked together by chains of atoms. The atoms in these chains may be all carbon atoms or they may be both carbon atoms and oxygen atoms or the chains themselves may consist of or contain carboxylic amide groups. It is found that to obtain polymers having the highest melting points and greatest resistance to solvents, the two chains linking any one ring to the rest of the polymer molecule should be attached to the ring at points as remote from each other as possible. Thus with six-membered rings, it is preferable for the linking chains to be attached to the rings at positions para to each other. With five-membered rings, if the position at which one chain is attached be numbered the 1-position, the other chain is preferably attached at the 3- or 4-position.

The theory underlying the formation of linear polymers from monomeric reagents containing 3, 4 or more reactive groups, while quite simple when applied to particular compounds or particular series of compounds, is nevertheless complex when considered in its broad aspects. The invention will therefore be illustrated by a series of examples, and the general principles underlying the invention explained with reference to those examples.

Broadly the invention includes two types of reaction designed to produce the linear polyamide having the carboxylic amide-containing rings.

(1) In this type of reaction, two amide-forming groups in one molecule unite with amideforming groups in another molecule to form a 5- or 6-membered ring. It is clear that this is not enough for the formation of the linear polymer, and the molecules must have additional amide-forming groups. These may likewise be such that rings are formed. For example, each molecule may have two pairs, 1. e. four, amideforming groups, and each pair may unite with a pair of amide-forming groups of another mole cule to form a 5- or 6-membered ring. This is the case for example with the a.a'-diaminosebacic acid and similar a.a'-diamino-dicarboxy1ic acids. Alternatively, the additional reactive groups may be single reactive groups in each molecule which unite together to form the linear polymer. An example of such a reagent is aspartic acid, two molecules of which may unite to form the lactimide, leaving available one carboxylic acid group from each molecule to form a linear polymer with a diamine.

(2) In a second type of process, the amideforming groups necessary for the formation of the ring are present in the same molecule, and

this molecule includes in addition two amideforming groups for the formation of the linear polymer.

A third type of reaction, in which a reagent containing two reactive groups is combined with a reagent containing four, six, eight, etc. reactive groups to form a ring or rings and at the same time to form the linear polymer, is described in application S. No. 583,841.

The invention will now be illustrated by reference tocertain broad types of monomeric reagents, and will be illustrated by specific examples showing the production of polymers using those reagents.

TYPE I One kind of starting material for this type of reaction consists of the aa'-diamino-dicarboxylic acids. These may be either au'-diprimary-amino-dicarboxylic acids or aa'-disecondary-aminodicarboxylic acids, or, of course, aid-primarysecondary diamino dicarboxylic acids. These aa-diamino dicarboxylic acids may be of the general formulae:

NHR; 00011 and RKE-I and We prefer to employ diamino-dicarboxylic acids which contain at least one primary-amino group. By this means the 2.5-diketo-piperazine ring which is formed contains at least one hydrogen atom attached to a nitrogen atom, or alternatively the polymer contains some rings in which both nitrogen atoms carry hydrogen atoms and other rings in which the nitrogen atoms carry no hydrogen. It is preferable to form rings in which the nitrogen atoms do carry hydrogen atoms, since it is found that not only does the presence of this hydrogen atom attached to the nitrogen increase the melting point of the polymer, but it also increases the resistance of the polymer to aqueous media, which is a very important consideration when the polymers are to be made into textile filaments. Suitable starting materials which are diprimaryamino-'dicarboxylic acids are 2.6-diamino-pimelic acid, 2.7-diamino-suberic acid, 2.8-diaminoazelaic acid, 2.9-diamino-sebacic acid, etc. Other suitable raw materials of this type include 2.3- diamino-succinic acid, in which case R in the first general fromula above is a direct bond. 2.4- diamino-glutaric acid constitutes a special case and will be discussed in more detail below. The chain joining the two pairs of amide-forming groups may, contain other atoms in addition to carbon. For example other suitable raw materials include a.a-diamino-diglycollic acidand cmdiamino dihydracrylic acid and homologues thereof. Such reagents may be made by the standard methods from the ether dicarboxylic acids, e. g. by bromination and replacement of the bromine by amino groups. Instead of using the carboxylic acids in the free state, their esters, halides, amides or (if water is present) nitriles, may be used.

The disecondary-dicarboxylic acids of the second. general formula above are conveniently prepared by condensing an organic diamine with formaldehyde or other aldehyde or ketone and hydrogen cyanide. This may be carried out by mixing the diamine hydrochloride, formaldehyde or other aldehyde or ketone and an alkali metal cyanide. By this reaction the dinitriles of dicarboxylic acids of the above type are produced, which may be hydrolysed to the carboxylic acids, 6. g. by means of baryta. While as with the ad'- diprimary-amino-dicarboxylic acid, the glycine or other a-amino-carboxylic acid residues may be united by a single direct linkage (joining in the present case the nitrogen atoms), it is preferable that their nitrogen atoms should be linked by a succession of methylene groups. Thus, for

example, it may be tetramethylene, pentamethylene, hexamethylene, decamethylene or the like, such starting materials being built up respectively from tetramethylene diamine, pentamethylene diamine, hexamethylene diamine and decamethylene diamine. The structural unit of the polymer from this type of starting material also contains the 2.5-diketopiperazine ring, but in this case the divalent organic radicle Joining the rings is united to the nitrogen atoms, whereas with the other type of ad-diamino-dicarboxylic acid, the divalent organic radicle is united to the carbon atoms of the diketopipera'zine rings.

Similarly, polymers containing 3.5-diketo-pyrazolldine rings or 3.6-diketopyridazine rings may l5 H000 OOOH be produced by condensing a dihydrazine with a bis-malonic acid or/a bis-succinic acid, the gen- NH-Jh-IL'H HOOC- H: Hr-COOH relatively difficult monomeric materiaisto work with, and hence it is diflicult to carry the condensation sufilciently far to produce a polymer of fibre-forming dimensions.

A further reaction of this same general type consists in condensing a dicyanhydrin with a. diurea, the polymerisation involving the elimination of ammonia and the production of a polymer containing the 2.4-diketodmidazoline or hydantoin ring, thus:

OO.N-R:NOO R. c l a C 1 R \NH- 0 \NH \R where R may be hydrogen alkyl etc, The dicyanhydrins for this type of reaction include, for example, aa'-C1iOXy suberonitrile and aa'-dl0Xy sebaconitrile and may be made by the addition of hydrocyanic acid to the appropriate dialdehyde, for example, and suberic dialdehyde, or to a suitable diketone. for example 2.7-octadione. The

diureas, for example tetramethylene diurea, pen tamethylene diurea, hexamethylene diurea and decamethylene diurea, are produced from the corresponding diamines by heating with urea, in which case ammonia is eliminated, or by simple addition of isocyanic acid. The above reaction is an instance of the use of a nitrile together with water as an equivalent of the corresponding carboxylic acid. In the present case the water is produced in the reaction between the hydroxy groups and the urea residues.

The same type of polymer, namely a polyhydantoin, may be obtained by condensing an ad.- diamino-dicarboxylic acid with a diurethane, a diurea or a di-isocyanate..

Suitable diamino-dicarboxylic acids are those described above with reference. to the production of polymers containing the diketo-piperazine ring. Again in the present case we prefer to employ the cw.-diprimary-amino-dicarboxylic acids, since by this, means each hydantoin ring contains a nitrogen atom carrying a hydrogen atom, with consequent improvement in the properties of the polymer. 'As suitable diurethanes, diureas and diisocyanates, those corresponding with ethylene, trimethylene, tetramethylene, pentamethylene and hexamethylene diamines may be used.

Polymers containing 2,4 diketo hexahydropyrimidine rings, i. e. polyhydro-uracils, may be produced by similar methods. In one method a bis-fi-imino-propionic acid is condensed with a diurethane, a diurea or a di-isocyanate. The equation in the case of using a diurethane is as follows:

R NH-O the rings may be produced by reaction between a 1 ,9.p-di-primary amino-dicar-boxylic acid or an '-diolefinic dicarboxylic acid and a diurea. p.p'- I diprimary-amino-dicarboxylic acids may be produced by reduction of the nitrile groups and, if desired, saponification of the ester grov s in alkylene bis-cyanacetic esters, prepared fro. an alkylene dihalide and two moles of mono-sodium cyanacetic ester. The diolefinic acids may be of the type HOOC.CH=CH.R1CH=CH.COOH where R1 is a divalent radicle or a direct bond as in muconic acid, homopiperylene dicarboxylic acid 7 HOOQCH=CH.CH2CH2.CH=CH.COOH, pp pphenylene diacrylic acid nooocu=onC -cn=cn.coon

and 5fi-2.2-diphenyl diacrylic acid for example tetramethyl fulgenic acid (di-isopropylidene succinic acid), a-t-diphenyl fulgenic acid (dibenzyiidene succinic acid) and aa-dimethyl-aa-diphenyl fulgenic acid. The reactions of the above 3.13-di-primary-amino-dicarboxylic acid and of the two types of dicarboxylic acid with the diurea are probably represented by the equations:

and

Further polymers within this general type of polymer are as follows:

(a) A diamidine is condensed with a diacetoacetic ester, according to the general equation:

to produce a poly-pyrimidone. The diamidlne is best used in the form of the hydrochloride, and the reaction carried out in the presence of caustic soda or other suitable base. The diamidines may be produced from the correspondester.

ing dinitriles, for example the dinitriles of adipic acid or its homologues, as mentioned above, by first converting to the bis-iminoether by treatment with hydrochloric acid and an alcohol, and then treating the bis-imino-ether with ammonia. In order to conserve ammonia, it may be desirable to neutralise, at least in part, the hydrochloric acid used in the preparation 01' the iminoether. This may be done with caustic soda, but, inasmuch as it is preferred to use the diamidlne hydrochloride in the final polymerisation, this neutralisation of the hydrochloric acid associated with the imlno-ether may be carried to a point short of liberation of the free imino-ether base. Suitable bis-aceto-acetic esters may be produced by a condensation of the sodium compound of aceto-acetic ester with dihalides, and

particularly polymethylene dihalides, for example tetramethylene dibromide, pentamethylene dibromide, hexamethylene dibromide and the like.

(b) A similar type 01 condensation consists in condensing a diamidlne with a bis-malonlc ester to produce a poly-diketo-tetrahydro-pyrimidine, according to the equation:

Here again it is desirable to carry out the polymerisation using the diamidlne hydrochloride in an alkaline medium, for example alkaline sodium ethylate. The bis-malonic acids may be produced in a manner similar to the bis-acetoacetic esters of polymer ((1) but using sodium malonic ester instead of sodium aceto-acetic Polymers of this type, that is to say polydiketo-tetrahydro-pyrimidines, tend to be of very high melting point, and consequently, in order to obtain tractable polymers, it is desirable that the divalent radlcles R1 and R2 in the above equations should together contain a relatively large number of methylene groups or equivalent groups; for example sebaconitrile may be used in the preparation of the diamidine and/or decamethylene dihalide may be used in the preparation of the bis-malonic ester.

A variant of the above reaction which produces the same type of polymer consists in condensing a bis-malonic ester with a bis-malonamide, according to the equation:

(0) Another type of polymer, namely a polyimidazolone, may be produced by condensing a bis-imido-ether, for example those produced as intermediates for the diamidines of polymers (a) and (b), with a bis -NN' Or a bis-CC glycine ester. We prefer to use bis-CC'-glycine esters, since the polymers resulting from them contain a hydrogen atom attached to'one of the nitrogen atoms in imidazolone ring. Suitable CC- glycine esters are the esters of 2.6-diaminopimelic acid, 2.7-diamino-suberic acid, 2.8-di- 15 amino-azelaic acid and 2.9-diamino-sebacic acid.

The production of'this polymer is represented by the following equation:

carboxylic acid containing an additional amino K group, for example, 2.3-diamlno-propionic acid, )(000 coon -HN Nn 2.3-diamino-n-butyric acid and 2.6-diamino- NI! Nll caproic acid (lysine). In this case 2 molecules of R R the diamino-carboxylic acid are condensed with l- 2"" y J 1 mole of a dicarboxylic acid to produce a polyl0 mer according to the equation As stated above, NN'-diglycines may also be NH, used, particularly where the desired application oi the polymers is not filament-formation. The production of the polymer from the NN'-dicoon glycine ester and the bis-imido-ether is repre- 1:; H000 sented by the equation! ClI-R -NH, BOOC-Rg-OOOH NHR1-NH R0 0R HIV Ha H: \C-B:-O/ (LOOR (BOOB EN -mNn.co-R,-0o.r-:a-Ric cn- -R N-CRr-CN-- CO.NH

on \N 1/ cn Here a i it i 1' b1 t 1 gan 5 pre era e o emp oy reagents b in which some, if not all, the amino groups are primary amino groups. Finally under this head Su b l lyclne esters for this Synthesis we may condense an a-amino-carboxylic acid are the esters of ao'-diamino-dicarboxylic acids containing an additional carboxylic acid group of this yp already referred to abovewith an a-amino-carboxylic acid containing an S Previously p n d, i S not essential f additional amino group. The same limitations this p I reaction far all the molecules in the apply to the position of the additional carboxylic reaction mixture to have four amide-fo acid and additional amino groups as referred to roups. A mil r yp polymer y be above, namely that they must not be in a lactamdu d y m a s of m u s containing nly forming position with another group in the same three amide-formin s oupswo out of these molecule. The equation for the production or the three amide-forming groups are designed to make polymer ad a f llows; a carboxylic amide-containing ring with a pair of Nm Ho 03 complementary amide-iorming groups in another molecule, and each of the molecules contains one 5000-31-0 additional amide-forming group for the purpose coon rim of producing the linear polymer. The molecules 40 NH-OO containing three amide-forming groups are preferably a-amino-carboxylic acids containing one g CH RT NH CO additional amide-forming group, which may be 4 either the amino type of group or the carboxylic In this type of reaction in which an o-aminotype of group. This additional amide-forming carboxylic acid containing an additonal amidegroup should not be in a lactam-forming position forming group is employed as one of the reagents, with one of the other amide-forming groups in the we find that where the a-amino group is a; prisame molecule. Thus, for example, glutamic acid mary amino group it is quite convenient to preon the one hand and ornithine (2.5-diamino-nform the lactimide by combining together the valeric acid) on the other, are not applicable for amino and oarboxylic acid groups which are this purpose. In the case of using an a-aminoalpha to each other in two molecules. Thus, for carboxylic acid containing an additional carexample, we may start from the lactimide formed boxylic acid group, the invention contemplates from two moles of aspartic acid, or again we may the use of two moles of the amino-dicarboxylic start from the lactimide formed from two moles acid with 1 mole of a diamine, the polymer being of 2.3-diamino-propionic acid. In the case of produced in accordance with the equation the lactimide from aspartic acid, it is quite conno0c-a,-c on-al-coon NH -Rg-NH,

coon H,

Suitable amino-dicarboxylic acids for this reaction are aspartic acid and a-amino-pimelic acid. t is not. essential for the amino groups to be primary amino groups, and such bodies as N- methyl-aspartic acid may be used. Preferably, however, some, if not all, the amino groups in the reaction mixture are primary amino groups, so that in the final polymer, as explained above, at least some of the amide nitrogen atoms carry a hydrogen atom. A similar type of reaction conl0 acid with 1 mole of diamine. In this case the amino-dicarboxyllc acid contains a secondary amino group. Similarly we may use an a-aminovenient to make this by simple treatment of diethyl fumarate with ammonia. By this means the diamide of the lactimide is produced which may either be used directly for condensation with a diamine, the polymerisation involving elimination of ammonia, or may be hydrolysed with a mild hydrolysing agent, such as baryta, to eliminate the amide groups without splitting the lactimide ring. Again, instead of using 2 moles of aspartic acid or 1 mole of the lactimide produced sists in condensing 2 moles of imino-bis-acetic from 2 moles of aspartic acid, we may use 1 mole Ezample I Diamino-sebacic acid, prepared by reaction of liquid ammonia with aa-dibromo-sebaeic acid or by hydrolysis of hexamethylene bis-phthalimido-malonic ester, waspurified by dissolving in caustic soda, warming with a little charcoal,

filtering and reprecipitating with hydrochloric acid. The pure-white product had C, 51.78%; H, 8.83%; N, 12.00%. CH20O4'N2 requires C, 51.69%; H, 8.68%; N, 12.07%. 5 parts and-diamino-sebacic acid were suspended in 40 parts absolute ethanol saturated with dry hydrogen chloride and refluxed for minutes. The acid dissolved to a clear solution from which the alcohol was removed by vacuum evaporation at 15 C. The residual solid was filtered off, washed with a little absolute ethanol and with ether and dried in vacuo, leaving 5.85 parts diamino-sebacic ethyl ester hydrochloride, as a colourless crystalline solid. Found: N, 7.83%; CI, 19.87%. C14H3004N2CI2 requires N, 7.76%; Cl, 19.63%. The ester hydrochloride could be purified by dissolving in a little warm ethanol and repreclpitating with ether.

The free diamino-diester was isolated by suspending parts of the ester hydrochloride in parts dry ethanol and adding a solution of 3.18 parts clean sodium in 40 parts absolute ethanol. The mixture was cooled to 0 0., filtered from sodium chloride, the alcohol removed under reduced pressure and the residual oil distilled at base temperature 150-60, pressure 0.005 mm. Hg, giving a colourless oil which partly solidified on cooling. Found: C, 58.55% H, 9.26%. C14H2aO4N2 requires C, 58.30%; H, 9.79%.

6.3 parts aa'-diamino-sebacic ester were heated in parts m-cresol for 6 hours at 205 C. in nitrogen. The polymer was precipitated by addition of excess ether, extracted thoroughly with hot ether and then with water and dried in vacuo at 50 C. It was partially soluble in m-cresol and in formic acid. Found: C, 61.47%; H, 8.66%.

NH-C o requires C, 61.20%; H, 8.22%.

Example II 72.6 parts of hexamethylene diamine in parts of water were cooled in ice and neutralised with concentrated hydrochloric acid and 86.8 parts of potassium cyanide in 120 parts of Water were added. 37 parts of formaldehyde (in the form of commercial forty percent formalin) were run into the stirred solution at'5-10 during 1 hour, the mixture held for 3 hours at room temperature, filtered and the hexamethylene bis-imino-acetoni trile thrown out as an oil by addition of '70 parts of solid potassium carbonate. The oil was separated, taken up in 200 parts of methyl alcohol, the solution dried over anhydrous sodium sulphate, treated with charcoal and filtered. (From this solution the hexamethylene bis-imino-acetonitrile dihydrochloride could be precipitated by ad dition of concentrated hydrochloric acid. Recrystallised from methyl alcohol it had M. P.

12 188-9. (dec.). Cl found 26.8%; C1oHmN4Cla requires Cl, 26.53%).

The methyl alcoholic solution of the nitrile was evaporated to dryness under reduced pressure, leaving the crude nitrile as a low melting, crystalline solid. This was taken up in dry ethyl alcohol and filtered from inorganic salts and the solvent removed.

84 parts of the nitrile, parts of barium hydroxide octahydrate and 3000 parts of water were refluxed for 13 hours, the barium precipitated by addition of the stoichiometric amount of sulphuric acid, the barium sulphate filtered off and the filtrate evaporated under reduced pressure until a considerable amount of the crystalline hexamethylene bis-imino-acetic acid had separated. This was filtered off and a further crop obtained by addition of ethyl alcohol to the mother liquors. The amino acid was purified by taking up in a small quantity of hot water and reprecipitating with ethyl alcohol. Hexamethylene bis-imino-acetic acid slnters at 257 and melts with decomposition at 265-6 (rapid heating). Found: C, 51.47%; H, 8.86%; N, 12.28%; C10H20N204 requires C, 51.69%; H, 8.68%; N, 12.07%.

3 parts of hexamethylene bis-imino-acetic acid, 7 parts of phenol or m-cresol and 1 part of 1% aqueous phosphoric acid were heated at 180 in a stream of pure nitrogen for 30 hours, additional phenol or m-cresol being added from time to time to make up for evaporation losses. Heating was continued at 218 for 20 hours, and finally at the same temperature for 3 hours at 18 mms. A tough polymer remained, from which fibres could be drawn at 255. These fibres were characterised by fairly high elasticity and a strong tendency to crinkle. The polymer was soluble in m-cresol, formic acid and acetic acid and could be purified by precipitation from m-cresol with acetone. On rapid heating in air the polymer meltedat about 235. Found: C, 61.25%; H 8.68%.

requires C, 61.20%; H, 8.22%.

' Example III Example IV 8.0 parts of aa'-diamino-sebacic ester were heated in hydrogen for 6 hours at 220 C. to give a solid, slightly yellow, polymer which did not melt below 280 C. and which was substantially unaffected by a large variety of solvents. On the other hand a mixture of 6.4 parts of diaminosebacic ester and 6.0'parts hexamethylene bisimino-acetic ester heated for 6 hours in 50 parts of m-cresol at 205 0. yielded a polymer which after precipitation by addition of ether melted at about 160' C. and could readily be redissolved in m-cresol. The hexamethylene bis-iminoacetic ester wasprepared as follows:

A suspension of 20 parts hexamethylene bis- The free Vbis-imino-dlester was prepared as in Example I. It distilled at base temperature 145-155 C., 0.005 mm. Hg. Found: C, 58.70%; N, 9.53%. C14N2aO4Nz requires C, 58.30%; H, 9.79%; N, 9.72%.

TYPE2 14 The left-hand polymer is the 2.5-diketo-piperazine type'or polymer, whilst the right-hand This type, as already explained, operates with a reaction mixture containing a reagent having four amide-forming groups, two of which are in a position such that a 5- or 6-membered carboxylic amide-containing ring can be formed.

to form the corresponding nitrile, and hydrolys-,

ing the nitrile. The polymer-forming reaction for this type of reagent is as follows:

CHa-CO This, however, is not the preferred kind of polymer under this type, since, as will be seen from the formula, the polymer contains no amide nitrogen atoms carrying hydrogen atoms. Another reagent which forms a polymer in which the amide nitrogen atoms do carry hydrogen atoms is aa'-diamino-glutaric acid. Theoretipolymer is the -butyrolactam type. So far we have been unable to assign a definite formula to the polymer produced from this monomeric reagent. It seems probable however that the polymer produced has the butyrolactam ring, 1. e. is a polymer of the right-hand formula.

Another raw material for this type of polymer may be built up from nitromethane and acrylonitrile or acrylic ester. The resulting nitro-tricarboxylic ester may be reduced by hydrogenation to the lactam dicarboxylic ester. In the case of condensing nitromethane with acrylonitrile, the nitro-trinitrile produced is first converted to the ester and then reduced. The

iactam di-ester may then be converted directly to the free acid followed by reduction leads to cally this body is capable of forming polymers 7 of Type 1 containing a 2.5-diketo-piperazine ring because it contains two pairs of amino and carboxylic acid groups in which the amino and carboxy groups are in the a-position in both cases, and in addition iscapable of forming polymers of the second type containing a 2-keto-pyrrolidine or 'y-butyrolactam ring because both amino groups are separated by three atoms from a carboxylic acid group. It will be seen that, having formed one lactani ring, the remaining amino and carboxy groups are sterically incapableof forming a further lactam ring and are therefore available for forming the linear polymer. two possible types of polymerisation of aa'-dlamino-glutaric acid are represented by the equations:

nooo-on-om-on-coon NH: NH:

The.

a mixture of the aminotricarboxylic acid and the lactam dicarboxylic acid. The series of reactions where reduction is carried out on the nitro-triester is represented asfollows:

02N.CCH:.CH:.CN

cnicnicN omomcoon o,N.c-cn,.crn.coon I cmcmdooa CHLCHLCOOR HN.G 0Ha.CHa.COOR

Suitable diamines for this condensation are ethylene diamine, tetramethylene diamine,

' -pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, decamethylene diamine, and the like.

A variant of the above method synthesis consists in forming a triamino-monocarboxylic acid for subsequent condensation with a dicarboxylic acid. j This may be achieved by first condensing the nitromethane with only one molecule of acryionitrile or acrylic ester, which is most efiiciently carried out by using an excess of nitromethane,

ester is then saponified to the free acid and condensed with two molecules of acrylonitrile. The

. is then hydrogenated or otherwise reduced so as dinitrile of a nitro-tricarboxylic acid so produced to reduce both nitrile groups and also the nitro group. The triamino-monocarboxylic acid thus produced may then be condensed with a dicar- 7-3 boxylic acid. The series of reactions for this synthesis using acrylonitrile throughout, is represented by the following equations:

omen, cn,=on.o. i o,N.on,.cn,.on2.ci\' M CH:.CH:.COOH

Suitable dicarboxylic acids for the final condensation are oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like.

In a similar way, acetone may be condensed with three moles of acrylonitrile or acrylic ester and the resulting monoketotricarboxylic acid derivative treated to convert the keto group to an amino group. This may be done by amidative reduction (e. g. after saponification of the trinitrile or triester) or by reduction of the keto group to a carbinol group, replacement of the hydroxy group of the carbinol by halogen, and replacement of the halogen by amino. The amino group in the resulting amino-tricarboxylic acid is then separated from each of the three carboxylic acid groups by four carbon atoms, so that it is in the position for forming a 2-ketopiperidine or t-valerolacta'm ring with any one of them. This amino-tricarboxylic acid is then condensed with a diamine. In the case of this synthesis from acetone, a variation may be carried out similar to that described above for the synthesis from nitromethane. Thus the acetone may first be condensed with one mole of acrylonitrile or acrylic ester (again carried, out most efliciently by using an excess of acetone). The resulting keto-nitrile is then saponifled to the free acid and condensed with two molecules of acrylonitrile, and the resulting compound then converted to a triamino-monocarboxylic acid by reduction of the two nitrile groups to amino groups and conversion of the keto group to an amino group.

Again under this head we may mention a synthesis in which methyl ethyl ketone is condensed with two moles of acrylonitrile or acrylic ester and the resulting keto-dicarboxylic acid derivative treated so as to replace the keto group by an a-amino-carboxylic acid residue, e. g. by treatment with ammonium cyanide or with bydrocyanic acid followed by ammonia. The nitrile group may then be reduced so as to. constitute a diamino-dicarboxylic acid in which one of the amino groups is separated from either carboxylic acid group by four carbon atoms and can therefore form a a-valerolactam ring with it, whilst the other amino group is separated by five carbon atoms from either of the carboxylic acidgroups and hence cannot form a 5- or 6- membered ring and is available with the other carboxylic acid group for forming the desired linear polymer. In this case it is unnecessary to use any additional reagent such as a diamine or dicarboxylic acid, since the diamino-dicar boxylic acid contains all the elements necessary for polymer formation. Instead of reducing the nitrile group, it may be saponified to constitute a mono-amino-tricarboxylic acid in which the ketobutanol or 3-ketobutanol.

Q Q 10 amino groups and either one of two of the carboxy groups are, as before, in the position for forming a S-valerolactam ring, while the remaining two carboxylic acids are available for condensing with a diamine in a way similar to that described above for forming a polymer from the amino-tricarboxylic acid obtained starting from nitromethane or acetone.

Another suitable synthesis for raw materials containing four amide-forming groups consists in starting from 2-acidyl-1-cyclohexanone or 2- acidyl-l-cyclopentanone or 2-acidyl 1 cycloheptanone. Preferably the acetyl compounds are used. These maybe made by condensing ethyl acetate or other acetic ester with the cyclic ketone in presence of sodium, sodium ethylate or the like. Other acidyl compounds may be produced by using the corresponding esters of other carboxyllc acids instead of the acetic esters. The 2-acidyl-cyclic ketones are then split by means of alkali to the corresponding keto-monocarboxylic acid. This keto-monocarboxylic acid is then condensed with one molecule of acrylonitrile, using the keto-carboxylic acid in excess so as to limit the condensation to one molecule of acrylonitrile, and the resulting nitrile saponifled to the ketodicarboxylic acid, which is then treated with ammonium cyanide, as before, to make an a-amino-nitrile. This series of reactions is represented by the equations:

CH1=CH.CN CH.CO.R --v R.CO.(CH2),.+1.COOH

| NG-CH:

Saponification Inthe above series of equations, the letter n represents 3, 4 or 5, and the symbol R may be any suitable alkyl or aryl group, but is preferably methyl. The resulting nitrilo-amino-dicarboxylic acid may finally be reduced to the corresponding diamino-dicarboxylic acid, which may be condensed with itself or may be saponified to the corresponding mono-amino-tricarboxylic acid, which may be condensed with a suitable diamine, as already described.

A further suitable synthesis for the raw materials starts with acetone or other suitable ketone of the formula R1.CO.CH2.R2 and condenses it with formaldehyde. In the case of methyl ethyl ketone and acetone, as described in U. S. applications S. No. 498,578 filed August 13, 1943 now Patent No. 2,378,988 and S. No. 498,100 filed August 10, 1943 now Patent No. 2,395,414, the reaction is preferably carried out with a very considerable excess of the ketone, for example up to 10 or 20 moles, so as to get a good yield of the 2-methyl-3- The keto-butanol may then be condensed with one molecule of acrylonitrile, the carbinol group converted to an alkyl halide group, for example by treatment with thionyl chloride, and the resulting compound then treated with ammonium cyanide to produce a mono-amino-trinitrile, which is then saponified crystals.

. with charcoal),

to the mono-amino-tricarboxylic acid. The

. series of reactions is represented by the equations:

R1 R3 nooc-t:-d-om.om.co oa NH: H:

in which R: may be any alkyl or aryl group. but is preferably either hydrogen or methyl, and R1 is preferably methyl. The resulting monoamino-tricarboxylic acid may be condensed witha diamine as before.

The following'examples illustrate the production of polymers of the general Type 2.

Example V most colourless. crystalline lactam, 5.5-di- (p-car- .boxyethyl) -pyrrolidone-2, M. 160-1", which after recrystallising from water, washing with acetone and drying in vacuo had M. 162, acid equivalent 15.25 parts of nitromethane, 1 part oi. sodium methylate and 16 parts of tert-butanol were heated to 60 and 53 parts of acrylonitrile, containing a trace of hydroquinone as stabiliser,

added with stirring during about 20 minutes at such a rate as to maintain the reaction mixture gently refluxing. Throughout this addition the external temperature was held at 60'70 C. The mixture was then refluxed, with stirring, for 30 minutes, the hot liquid made slightly acid with dilute hydrochloric acid and three times its volume of water added with stirring. A dark mass' separated which was boiled with the motor liquors. On cooling a dark tarry material separated, together with a quantity of light brown The crystals and mother liquors were decanted oil, the crystals separated and the mother liquors used to extract the tarry material at the boil. Repetition of this process five or six times, finally with the addition of activated charcoal, gave 27.8 parts of crude, crystalline tri- (fl-cyanoethyl)Fnitromethane' M. 112-5. This was purified by recrystallisation from water yield 24.9 parts, M. 115.- I'ound: C, 54.6%; H, 5.68%; N, 25.6%.

requires C, 54.55%; H, 5.49%; N, 25.45%.

11 parts tri-(p-cyanoethyl) -nitromethane were refluxed with 65 parts 20% hydrochloric acid for 6 hours. On cooling the mixture deposited the crystalline tri (,e-carboxyethyl) -nitromethane, which was filtered, washed with cold water till free from ammonium chloride and hydrochloric acid and recrystallisedfrom hot water, yield 12 parts, M. 187. Found: acid equivalent 92.4; C, 43.25%; H, 5.55%: N, 5.00%. C1oH150sN requires acid equivalent 92.4; C, 43.32%; H, 5.45%; N, 5.05%.

25 parts of trl-fi-carboxyethyl nitromethane, 200 parts water and 7 parts of Raney nickel were shaken at 110 for 1% hours in a stainless steel autoclave under a hydrogen pressure of 2500 lbs. The reaction-mixture was filtered, evaporated under reduced pressure almost to dryness and acetone added, when a small amount oi. nickel complex, of probable formula 115.3; C, 52.20%; H, 6.49%; N, 6.17%. requires acid equivalent 114.6; C, 52.40%; H, 6.60%; N, 8.11%.

The mother liquors separated from the lactam were evaporated to dryness under reduced pressure leaving 9 parts of amino acid, CCC-(tri-fi= carboxyethyD-methylamine, M. (partial) 83, acid equivalent, 121.7; CloHnOeN requires acid equivalent 123.6. Recrystallisation from water yielded a purer product M. (partial) 824, acid equivalent 123.7; N, 5.62%; CioHnOcN requires N, 5.67%. The absence of a sharp melting point is attributed to transformation to the lactam. Crystallisation of-the amino acid from boiling ethanol or butanol yielded the lactam while on boiling the latter with water for 15 minutes partial transformation to the amino acid occurred.

6 parts of CCC-tri-B-carboxyethyl-methylamine and 4.2 parts diformyl-hexa-methylene dlamine were heated in hydrogen for 2 hours at 255, hour at 278 and 1 hour at 278/0.5 mm. A clear, slightly brownish polymer was obtained .from which fibres could readily be drawn. It

melted at about and was soluble in formic acid, ethanol and m-cresol, the intrinsic viscosity in 1% solution in the last solvent being 0.50.

Similarly on heating the amino tricarboxylic acid with 1 mole of hexamethylene diamine at 278 for A, hour, and at 278/0.5 mm. for /2 hour there was obtained a polymer intrinsic viscosity, 1% in'm-cresol, 0.32.

Example v1 The triethyl ester of tri(p-carboxy-ethyl) nitromethane was prepared as follows: 8 parts of the acid prepared as in Example V above were refluxed with 65 parts of 3% absolute ethanolie hydrogen chloride for 16 hours, most of the alcohol distilled off and the residue diluted with aqueous sodium carbonate and sufficient ether to ensure good separation into two layers. The ethereal layer was washed again with carbonate solution, then with water, dried over sodium sulphate and the ether removed. The residual material was distilled at 0.002 mm. Hg at a base temperature 0., yield 8.3 parts tri-(fi-car bethoxy-ethyl)-nitromethane as a colourless, rather viscous oil n l.4620. Found: C, 53.13: H, 7.33%. CmHz'rOsN requires C, 53.16; H, 7.53%.

20 parts tri-(p-carbethoxyethyl)-nitromethane, 80 parts of alcohol and 5 parts of Raney nickel were shaken in a stainless steel autoclave ,Qat 170-190 for}; hours under a hydrogen pres-Q base temperature 180-195".

11.4 parts 5.5-di-(B-carbethoxyethyl)-2-pyrrolidone and 6.9 parts decamethylene dlamine in 30 parts of ethanol were heated in hydrogen, at first at a moderate temperature permitting slow removal of alcohol and later for 2 hours at and 1 hour at -255/1 mm. The polymer remained as a hard brown glass, soluble in ethanol,

CioHisOeN Example VII parts of 5.5-di-(fi-carboxyethyl) -2Dyrrolidone prepared as in Example V above and 7.5 parts of diformyl-hexamethylene diamine were heated in hydrogen for 4 'hours at 255 and 3 hours at 255/1.0 mm. The polymer, a hard brown, clear glass, melted 160-5 C.- Long fibres could readily be drawn from the melt. The intrinsic viscosity (1% in m-cresol) was 0.66.

, The invention includes the production of mixed polymers by using appropriate mixtures of difi'erent reagents of the same or of diilerent types. This as illustrated in Examples III and IV above, mixtures of different a-a' diamino dicarboxylic acids may be co-polymerised. Again in condensing two molecules of aspartic acid with one molecule of a diamine, two or more different diamines may be used, the quantities used together making up the molecular proportion required. Similarly an aminotricarboxylic acid of the type of tri(fi-carboxyethyl) -methylamine may be condensed with an equimolecular proportion of a mixture of two or more different diamines. Generally the effect of such co-polymerisation is to lower the melting point and increase the solubility as compared with the simple polymers.

As will be seen from the above examples both of the Type I and of the Type II polymers the polymerisation is carried out simply by subjecting the raw materials to the ordinary amideforming conditions, for example by heating generally to temperatures of the order of ISO-300 C. The condensation is continued until the polymer has the desired molecular weight. One of the principal purposes of the present invention is to produce polymers which are fibre-forming. This simply means that the condensation is continued until a test shows that the polymer can form fibres. For example, when carrying out the condensation in the melt, a rod may be dipped into the molten polymer and drawn away to ascertain its fibre-forming properties. Generally the condensation may be carried out with or without a diluent. in the former case preferably while melting the monomeric substance or the low polymers obtained after the condensation has been carried some way. Where a diluent is used, it is preferably a solvent for the resulting polymer, for example a phenolic solvent such as phenol itself, the cresols and xylenols. Conveniently the solvent or diluent is so chosen that it boils at the desired polymerisation temperature, so that the condensation. at least in its initial stages, may be carried out at atmospheric pressure while boiling. In

the case where a volatile body such as water or ethyl alcohol is split ofi' during the condensation, it is desirable, as the condensation proceeds, to apply vacuum or alternatively a current of inert gas, so as to promote the condensation. It is sometimes desirable to employ a condensation catalyst with a view to carrying out the reaction at a lower temperature than would otherwise be possible. This seems to be especially advantage-' ous where a secondary amino group is to be reacted with a carboxylic group. A very small proportion of phosphoric acid, for example of the order of .01 to .1% of the reagents, is usually sufficient for this purpose. To avoid discolouration, it'is in all cases desirable to exclude air, so that the condensation may, for example, be carried-out in the presence oi oxygen-free nitrogen, hydrogen or other inert gas.

The carboxylic acid 'may be used in the free state or in the form of an ester or halide or amide or (if water is present) as nitrile. Similarly, instead of using the free amino groups, acldylamino groups containing acidyl groups which are readily replaced, for example the formyl radicle,

may be used.

As previously stated, in the case of a single starting material or series of starting materials, it is relatively easy to determine whether or not it is a suitable material for the purpose of the present invention. The general considerations are, however, somewhat complex. In the case of polymers of Type 1 which carry a pair or two pairs of amide-forming groups in which the individuals of the pair are adjacent to each other and this pair of amide-forming groups is to react with a corresponding pair of complementary amideforming groups in another molecule, as already stated, the position of the individuals of each pair with respect to each other must be such that a 5- or 6-membered ring may result. It is customary in this art to refer to radicle lengths of molecules or pairs of molecules. The radicle of oxalic acid, for instance, is CO.CO-, that of carbonic acid is CO, and that of ethylene diamine is -NH.CH2.CH2.NH. The radicle length of oxalic acid is thus 2, that of carbonic acid is 1, while the radicle length of ethylene diamine is 4. Using this terminology, the radicle length of the amino group with respect to the carboxylic group in an a-amino-carboxylic acid is 3. When, therefore, an a-amino-carboxylic acid is condensed with itself or another a-amino-carboxylic acid to form a 2.5-diketo-piperazine ring,- the sum of the two radicle lengths is 6. In other words, the sum of the radicle lengths of the two pairs of complementary reactive radicles is the sum of -the number of atoms in the ring to be formed. Hence, in the reagents of the present invention, which contemplates the production of carboxylic amide-containing rings having 5 or 6 atoms in the ring, the sum of the radicle lengths of the pairs of amide-forming radicles designed must be so separated from each other that they cannot form another 5 or G-membered ring. v Another way of looking at the matter is to consider the formation of the linear polymer and of the carboxylic amide-containing ring as two separate operations. This will be illustrated by reference to the formation of polymers already referred to above (a) From an ad-diaminodicarboxylic acid of each type, and

(b) From two molecules of aspartic acid with one molecule of a diamine, and

(c) From one mole of the amino-tricarboxylic -.acid obtained from nitromethane and acrylo-= nitrile together with one mole of diamine.

In each case it may be considered that one of the reactions involved consists in forming the linear polymer. In the case of the first type of 21 u'-diamino-dicarboxylic acid, the linear polymer (before ring formation) has the arrangement In the case of the second type of reagent, e. g. the polyinethylene bis-imino-acetic acid type, the molecules after condensation to form the linear polymer but before ring formation, are of Again, in condensing two moles of aspartic acid, the condensation to produce the linear polymer (without ring formationi may be considered to take place according to the equation l coon H N Finally, one part of the condensation of CCC-tricarboxyethyl methylamine with one mole of diamine may be considered to take place according to the equation N 1 OH,

HO OC-C-Hr It will be noted that each one of these linear polymers contains an amino group and a carboxylic acid group in a position separated from each other by three or four atoms, so that they are able to form the 5- or 6-membered carboxylic amide-containing ring which forms an important part of the polymers of the present invention. This view of the matter serves to elucidate the principles on which the raw materials are selected for the purpose of the present invention, but it is not intended to suggest that the condensation actually takes place with the formation of a linear polymer first, followed by ringclosure. The principles to be followed in the selection of the positions of the amide-forming groups for the formation of the linear polymer (i. e. apart from the ring formation) are already well known. Thus, in the case of using an amino group and a carboxylic acid group in the same molecule, it is known that these groups should not be separated from each other by three or four atoms if a linear polymer is to result. Similarly, in the case of using two amino groups in one molecule and two carboxylic acid groups in another to form the linear polymer, it is recognised that the combined radicle lengths of the diamine and the dicarboxylic acid should not be less than 7, and further'the dicarboxylic acid should not have a radicle length of 4, because of the tendency to form rings of the succinimide type. The same considerations apply to the positioning of the amide-forming groups in the raw materials of the present invention insofar as these amide-forming groups are to form the linear polymer. Thus, the present invention utilises the known principles of forming linear polythese principles additional principles designed capable for forming the linear polymer. additional amino and carboxy groups are still prevent the formation of two rings.

to give rise to the ring formation at the same time as the formation of the linear polymer. There is one further point, however, with regard to the known limitations upon forming linear polymers from amino-carboxylic acids or their diamines and dicarboxylic acids. In the present invention, steric influences sometimes remove restrictions already present in the known art.

Thus, in the known art, in order to form a linear polymer from an amino-carboxylic acid, it is not possible to use anamino-carboxylic acid in which the amino and carboxy groups are separated by three or four carbon atoms. This restriction is not always present in the raw materials of the present invention. aa'-diamino-glutaric acid has already been referred to as a raw material which contains one amino group and one carboxylic acid group which are capable of forming a carboxylic amide-containing ring and containing an additional amino and carboxy group which are These separated from each other by three carbon atoms, but, owing to steric hindrance, they are not capable of forming a ring and are therefore available for forming the linear polymer. This case is quite different from the case of p -diamino-adipic acid, in which each amino group is separated from a carboxylic acid group by three carbon atoms, and can therefore form a butyrolactam ring, and steric influences do not The (iilactam of pfi -diamino-adipic acid is a known compound.

Where, as in the condensation of two molecules of aspartic acid with one molecule of diamine or in the condensation of one molecule of diamine with one molecule of'the aminotricarboxylic acid from nitromethane and acrylonitrile, two different kinds of reagents. are used in the production of the polymer, the ultimate molecular weight of the polymer may be determined by the exact proportion in which the reagents are used. A small departure from the proportions mentioned serves to limit the average molecular weight which may be achieved. Thus the diamine may be used in a slight excess over one molecule or in a quantity slightly less than one molecule (the other reagent being then in slight excess). By this means it is possible to predetermine the maximum average molecular weight which may be produced. By using this device the polymer is at the end of the polymerisation stable as regards its viscosity and is not liable to undergo further polymerisation on heating. Generally the molecular excess or deficiency to be used is of the order of 1-5% above or below the stoichiometric proportion in order to obtain polymers which are fibre-forming. 'The smaller the difference between the actual proportion used and the stoichiometric proportion, the higher will be the average molecular weight of the polymer and the higher its viscosity.

The above polymers may likewise be viscosity stabilised by inclusion in the reaction mixture of a small proportion of a substance containing a single amide-forming group. Such substances are preferably relatively-non -volatile, for example long chain aliphatic monoamines or monocarboxylic acids, e. g. dodecylamine, octadecylamine, lauric acid or stearic acid, though monoamines or monocarboxylic acids of lower molecular weight may be used. The molecular proportions in which such substances should be used are oi the same order as the molecular excess of diamine mentioned above.

In the case of the aa'-diaminodicarboxylic acids WhlCh are condensed with themselves a similarly small proportion of an a-amino acid, such as glycine or a-alanine, may be used as viscosity stabiliser.

The invention includes not only the production 01' the linear polymers, but also the production therefrom oi filaments, films and other articles. In forming filaments, the choice of the method of spinning dep nds in part on the properties of the polymers. vents can readily be produced, dry spinning methods may be employed with solutions in volatile solvents, and wet spinning methods with solutions in volatile or even comparatively non-volatile solvents. The polymers can be spun by melt spinning methods, 1. e. by extruding a melt o! the polymer through suitable orifices. In general, the temperature of the polymer to be extruded should be some -30" above the melting point of the polymer. This melting temperature may be modifled to some extent by mixing the polymer with suitable proportions of plasticisers, for example sulphonamide plasticisers, phenolic plasticisers, urea and thiourea plasticisers and the like. Such plasticisers may either be left in the products or may be partially or completely extracted therefrom.

The filaments so formed may be drawn out at comparatively low temperatures, or even at atmospheric temperature, to very fine filaments having high tenacity and good elasticity. The resulting filaments may then be used for any of the purposes to which artificial silks have in the past been applied.

Where solutions in organic sol-' While the invention is especially directed to the manufacture and application of fibre-forming polymers, it is not limited thereto and embraces the production of similar polymers suit able, for example, for use as softening agents, coatings, film-forming substances, and the like. Moreover, for these applications the polymers of the present invention may be mixed with other fibre-forming, film-forming or lacquer substances or other ingredients, for example cellulose acetate, aceto-butyrate, butyrate and aceto-stearate, ethyl cellulose, oxyethyl cellulose, oxyethyl cellulose acetate, benzyl cellulose and other cellulose derivatives, plasticisers or softening agents, dyestuffs, pigments and the like. The expression "liquid phase is used in the claim to connote that the reagents are molten or in solution in a liquid solvent.

REFERENCES CITED The following references are of record in the file of this .patent:

UNITED STATES PATENTS Number Name Date 2,341,611 Hagedorn et al Feb. 15, 1944 2,343,808 Schlack Mar. 7, 1944 2,389,662

Fisher et a1 Nov. 27, 1945 

